A real-time bulk material analyzing system is disclosed for analyzing the elemental characteristics of bulk material being transported on a conveyor belt.
Conveyor belts are extensively used to transport bulk materials such as Limestone, Bauxite, Copper ore, Zinc ore, Lead ore, Iron ore, Silica, Phosphate rock, Potash, Clay, Rare earths, Scrap materials, Chalk, Coal and coke, Alumina, Marl, Pyrite, Fly ash, etc. A conveyor belt includes two end pulleys, with a continuous belt that rotates about them in a continuous unending loop. The pulleys are powered, moving the belt and the loaded bulk material on the belt forward at fixed or variable speeds. Certain industrial applications require analyzing the exact or averaged composition of the bulk material which is transported on conveyor belts from one process point to another.
Bulk Materials are normally characterized in their raw material (pre-blended) states or following a blending (physical mixture of component raw materials) procedure via a system of proportioning feeders from bins or silos containing relatively homogeneous compositional characteristics.
Analysis of either raw material components or blended materials has been accomplished by extracting samples and transporting them either manually or via an automatic “tube post” pneumatic sampling and conveying system to a central laboratory for analysis where they are subject to analysis. The results are then communicated to a variety of means for adjusting proportions to meet e.g. a desired blend recipe.
This arrangement, while providing high accuracies, cannot meet the needs of real-time analyses for rapid and real-time control, as the time required for sampling, splitting, transport, preparation, and analysis can vary from a minimum of several minutes to an hour or more. During this delay, the fast-moving materials represented by the sample analyzed have long passed points of control and adjustments which are then made in response to results from the analysis of the samples might be inadequate or simply too late for corrective actions taken.
A basic solution sought by the bulk material processing industry is to analyze the materials as they pass through, or are exposed in some manner, to analytical systems while the materials remain both physically and chemically unchanged and pass uninterruptedly on their bed located on the moving conveyor belt. No attempt to stop or otherwise slow the speed of the conveyor belt merely to accommodate analysis is normally desired nor permitted as a necessary restriction on allowing production and processing in such production environments.
A few methods to achieve elemental, and thereby, oxide forms of the chemical constituents of the various raw or blended materials have been put into current practice. They are however limited in numbers in terms of practical application and are mainly making use of neutron activation systems. These so-called Prompt Gamma Neutron Activation Analysis (PGNAA) systems require either radioactive isotopes for neutron flux, such as the isotope of Californium, Cf252, or a neutron generator (tube). Neutron activation systems apply a potentially hazardous to humans technique which requires protective permanent careful shielding to humans via direct or indirect exposure and costly isotope or generator tube replacements. The short half-life of Cf252 at only approximately two and a half years and the requirement for replacement of neutron tube generators, normally every one to one and a half years, represent both expensive maintenance costs as well as difficulties in convincing authorities of the safety in transport and operation of both these neutron sources. Further, the resultant gamma radiation from the analyzed bulk materials, which is caused by neutron activation of the nuclei of the irradiated materials, represents additional health and environmental hazards.
Other techniques that have been attempted, such as high-power X-ray systems, or X-ray diffraction systems, also involve strict adherence to local regulatory authorities. In some venues, the presence of such devices is prohibited altogether.
US 2003/0123056 discloses a hyperspectral imaging instruments array for exploiting detailed multispectral, hyperspectral and ultraspectral imaging and non-imaging signature information. This is accomplished in real-time in order to identify the unique spectral characteristics of the target. The instruments array contains at least one mechanically integrated hyperspectral sensor installed on a fixed or moveable hardware frame and co-boresighted with a similarly mounted digital camera, calibrated visible light source, calibrated thermal source and calibrated fluorescence source on a small spot on the target. The target is moved across the array, allowing the array to effect collection of absolute radiometrically corrected spectral data against the target at high spatial and spectral resolutions.
As hyperspectral imaging spectrometers cannot penetrate to depth hyperspectral imaging has not been considered a practical means for real-time elemental bulk material analysis.